• Have been fully informed about the study and have voluntarily signed the ICF;

• Patients diagnosed with relapsed/refractory acute leukaemia (including AML, ALL, and mixed-phenotype acute leukaemia, excluding acute promyelocytic leukaemia) according to the World Health Organization (WHO) criteria in 2022, with bone marrow morphological changes (blasts/immature cells ≥ 5%), and who have been evaluated by the investigator to have no better treatment options, must meet at least one of the following conditions:

‣ Primary refractory disease, newly diagnosed disease that show no response after 2 cycles of standard treatment;

⁃ First relapse, relapsed within 12 months after CR/CRh/CRi following consolidation/intensive therapy;

⁃ Relapsed after 12 months and unresponsive to conventional salvage chemotherapy;

⁃ Patients with 2 or more relapses;

⁃ Patients intolerant to intensive chemotherapy who experience disease progression during continuous low-intensity therapy; Note: Patients with secondary AML or AML transformed from MDS, MPN, can also be enrolled, but they need to meet the above criteria after the disease has transformed into AML;

• For all Phase I patients, the presence of NPM1 mutation, or KMT2A rearrangement, or NUP98 rearrangement must be confirmed,During Phase I, patients with other acute leukemia subtypes shown to depend on menin-KMT2A interaction (e.g., UBTF-TD) or driven by HOXA/MEIS1 overexpression may also be eligible after consultation with the Sponsor's Medical Monitor;

• Patients in the Phase II (single-arm pivotal clinical study) must have a confirmed NPM1 mutation or KMT2A rearrangement. Enrollment based on local testing results is acceptable with a copy of the test report provided; however, all patients are required to submit screening bone marrow samples to the central laboratory ,Eligible NPM1 mutations include exon12 type A, B, and D mutations ; other NPM1 mutations causing cytoplasmic localization require sponsor pre-approval for enrollment. KMT2A rearrangements exclude non-fusion rearrangements involving KMT2A partial tandem duplication (KMT2A-PTD).

• Peripheral blood white blood cell count ≤ 35 × 109/L (use of hydroxyurea to control peripheral white blood cell count is permitted);

• Age ≥ 12 years (for adolescent patients aged 12 years or older but not yet 18 years old, weight must be ≥ 40 kg);

• ECOG score 0-2;

• Adequate hepatic, renal, and cardiac functions

• Expected survival of more than 12 weeks as judged by the investigator

⁃ For patients with D-dimer test results \> 5 × ULN during screening, relevant tests (such as rechecking coagulation function after a certain interval, lower extremity deep vein ultrasound, etc.) are required to exclude deep vein thrombosis, hypercoagulation, and disseminated intravascular coagulation before enrollment;

⁃ Able to undergo treatment, visits, and study-related examinations as required by the protocol;

⁃ Female patients of childbearing potential or male patients whose female partners are of childbearing potential must agree to use effective methods of contraception during the study and for 30 days after the last dose of study drug, such as double barrier methods, condoms, oral or injectable contraceptives, intrauterine devices, etc. Postmenopausal women (\> 45 years old and amenorrheic for more than 1 year) and surgically sterilized women are not subject to this condition.